The present invention relates to end closures for beer and beverage containers; and, more specifically, easy-open container ends having a large-opening panel with a smooth rupture of the score during opening by the user.
Typical end closures for beer and beverage containers have an opening panel and an attached leverage tab for pushing the opening panel into the container to open the end. The container is typically a drawn and ironed metal can, usually constructed from a thin plate of aluminum. End closures for such containers are also typically constructed from a cutedge of thin plate of aluminum or steel, formed into a blank end, and manufactured into a finished end by a process often referred to as end conversion. These ends are formed in the process of first forming a cutedge of thin metal, forming a blank end from the cutedge, and converting the blank into an end closure which may be seamed onto a container.
These types of container ends have been used for many years, with almost all such ends in use today being the xe2x80x9cecologyxe2x80x9d or xe2x80x9ceasy open stay-on-tabxe2x80x9d ends in which the tab remains attached to the end after the opening panel is opened. Throughout the use of such ends, manufacturers have sought to save the expense of the metal by downgauging the metal of the ends and the tabs. More recently, manufacturers have sought to provide container ends that have larger openings even as the overall diameters of the container ends have been reduced.
Because ends are used for containers with pressurized contents and/or contents that require heat treatment of pasteurization, the score of the opening panel must have sufficient score residual to withstand such pressure, which in turn requires that the tab have a thickness of metal to provide strength to open the panel. This produces a limitation to the desired metal reduction sought by manufacturers. The tab must have a thickness that imparts strength for opening the end member, and which provides reliability for opening the tear panel opening of the end member.
The more recent popular use of large-open ends provides additional difficulties for openability of the ends. Because of the enlarged size of the opening tear panel, at least in part resulting from the geometry of the score-line (as the opening is defined by a score with a greater width in the space between the rivet and the outer periphery of the panel), more stress is placed on the tab during opening of the tear panel of the end. This constrains efforts to further down-gauge the tab, and causes certain inconveniences for the user when opening the can. One example of this difficulty is presented due to the geometry of the large-opening end having an expanded width of the tear panel. The tear panel of the large-opening end has an expanded width due to the limited space available for the placement of the tear panel between the central rivet and the outer edge area of the end. Because of this geometry and the limitations of the tab placement on the end, the large-opening ends usually have tear panels that have regions more difficult to open by the tab leveraging against the tear panel. This is especially true for the region of the score which is in the 4:00 to 6:00 clock position, with the area of the tear panel closest the rivet being the 12:00 placement (and the 12:00 to 6:00 orientation of the tear panel is defined along a central axis of the tear panel passing through the rivet, the tab nose and the opposed lift-end of a typical arrangement).
The 4:00 to 6:00 region of the score peripheral geometry, and especially the 5:00 region, will typically include a curvilinear shaped segment with a relatively sharp radius of curvature to direct the tear panel score-line back toward the hinge segment to form a complete loop. This geometry presents resistance to the fracture of the score residual of metal in that region of the tear panel. Also, with the 4:00 to 6:00 region of the score geometry being a score segment located relatively distant from the tab nose, and thereby being further from the application of the opening force applied by the user, the user must apply additional leverage force by the tab to gain the needed force to continue the fracture of score in that distal region. Further, when the score of the typical tear panel in the 4:00 to 6:00 region is ruptured during opening, the shape of the tear panel requires displacement at an angle outward of the axis of the tab. The angular deflection of the tear panel is then shifted across the tab axis as the 4:00 to 6:00 region is fractured. This requires an additional amount of leverage by the tab nose to continue the opening of the tear panel relative to the initial areas of the tear panel.
When experiencing such resistence to openability, the user typically compensates by sustaining and increasing the lifting force of the tab, thereby pushing the nose of the tab harder on the tear panel. In this typical situation, the force on the tear panel continues until the resistance to opening is overcome, and the score quickly fractures past the 4:00 to 6:00 region and the opening of the tear panel is completed. Such a sequence of resistance, opening-force increase by the user, and rapid fracture of the score, results in the tear panel to quickly open past the 4:00 to 6:00 region. This causes the tear panel to quickly bend into the container toward the container contents. The result the tear panel slapping onto the liquid contents, which splashes the liquid contents upward to exit the opening as a xe2x80x9cspitting,xe2x80x9d or xe2x80x9cspewingxe2x80x9d of the liquid contents from the opening in the can end.
Another problem with large-opening container ends is the restriction to the material and cost savings when seeking to make the ends from a thinner metal stock (down-gauging). This is primarily due to the fact that the geometry of the tear panel, and the limited space between the rivet and outer panel edge. Because the typical tear panel for a large-opening end is generally symmetrical when divided through the central axis, the tear panel shape may require one to make the ends from a larger cutedge of metal to provide the space needed for the tear panel. For example, one design constraint that limits panel down-sizing is that such down-sizing, which leaves less space for the tear panel between the rivet and the outer peripheral edge, leads to the need for a sharper (smaller) radius of curvature at the 5:00 region of the tear panel. As the panel size is reduced, less space is available for the tear panel and smaller radius of curvature is required. Therefore, there is a need for a score panel geometry that provides a large opening that does not require a sharp radius in the 5:00 region.
As is explained in greater detail below, the present invention reduces or eliminates these problems with container ends. The present invention provides variations for overcoming the specific difficulties associated with design, manufacture and use of large-open beverage container ends.
It is an object of the present invention to provide a retailed-tab xe2x80x9cecologyxe2x80x9d container end member having a displaceable tear panel defined by a frangible score and a non-frangible hinge segment and in which the tear panel has a geometrical arrangement adapted to facilitate smooth opening of the end without substantial resistance to opening. The frangible score has an outer periphery defined by a curvilinear score length and a score residual thickness adapted to fracture when subject to opening force applied by the tab nose caused by a lifting of the tab lift end. The tear panel has a mid-sectional width defined along a cross axis residing perpendicular to a sectional axis, and in which the sectional axis and said cross axis divide the tear panel into four separate quadrants. The score length has an enlarged radius of curvature in the second quadrant relative to the radius of curvature in the first quadrant. It is also an object of the invention to provide an end member in which the first quadrant is positioned adjacent the tab and at a vent region of the tear panel, and the score of the first quadrant is curvilinear with a radius of curvature greater than a radius of curvature of the score in the third quadrant.
It is another object of the invention to provide a container end member with a central panel wall with a tab secured to the public side and a central longitudinal axis the tab nose and the opposed lift-end. The central longitudinal axis defines a division between a first side from that of a second side, wherein a displaceable tear panel has a tear-drop shape with a first-more narrow portion on one side of the axis and a second wider portion located on the other side of the axis.
It is further an object of the present invention to provide an end member with a displaceable tear panel defined by a frangible score with a central longitudinal axis along a 12:00-6:00 clockwise reference line, and with a radius of curvature in a 5:00 region that is greater that radius of curvature of the score in an 8:00 region. It is also an object for the tear panel of the end member to have an enlarged radius of curvature in the 4:00 to 5:00 region that is larger than the radius of curvature along other portions between the 2:00 to 10:00 regions of the score periphery. It is also an object of the invention to provide an end member with an enlarged radius of curvature at the second curved segment that is configured to provide minimal resistance to the fracture of the score by application of the opening force by the user. The structure of the end member score shape, and the method of making the same, provides ease of opening of the tear panel that reduces resistance to opening, especially in the 5:00 region of the score shape. This reduces the slapping of the tear panel into the container during opening of the tear panel, and provides a geometry of the score for smooth openability by minimizing resistance to score fracture, especially the score fracture at the curved segment located between the vent area of the score and the area closest to the outer peripheral edge of the end member.